Continuing advancements in electronic technology have led to the development of touch sensing technology for registering positional information and receiving user input. Within the broad category of touch sensing technology there exist capacitive sensing touch sensors, commonly referred to as capacitive touchpads (or simply touchpads) or capacitive touch screens (or simply touch screens).
In one type of conventional capacitive touchpad, capacitance sensor electrodes are arranged grid-like in rows and columns underneath a surface, with the row sensor electrodes and the column sensor electrodes separated by electrically insulating material. In one approach, a known voltage change can be first applied to the sensor electrodes of the rows, and then the sensor electrodes of the columns, in rapid succession. The touchpad has a sensing region in which it detects input. When an object is in the sensing region of the touchpad, the sensor electrodes within sensing range of the object will experience a change in the amount of electrical charge they are carrying due to capacitive coupling with the object—the sensor electrodes closest to the object will experience the largest change. The position of the object in one dimension can be determined by identifying the location associated with the column sensor electrodes experiencing the largest change in electrical charge, and similarly the position of the object in a second dimension can be determined by identifying which of the row of sensor electrodes experience the largest change in electrical charge. Alternatively, interpolation can further provide more detailed resolution of the positions. In this manner, the object's position relative to the sensing surface can be unambiguously determined.
In one method of manufacturing capacitive touchpads like the one just described, first the rows of sensor electrodes are formed on a substrate, then a layer of insulator is applied, and then the columns of sensor elements are formed on the insulator. The number of steps required can increase manufacturing costs and ultimately the cost to consumers. A capacitive touchpad that can be produced less expensively, but that can still unambiguously determine an object's position in two dimensions, would be of value.